Many marine and terrestrial animal species have proven difficult to study in their native habitats because of their complex behavioral patterns and the inhospitable environment in which they live. Many species exhibit an unnatural reaction to the presence of their human observers, while still others enjoy such a vast and varied habitat that first-hand observation by humans is highly impractical if not impossible, making the task of studying them that much more difficult. These and related factors have severely hindered mankind's ability to understand basic biology and the conservation needs of certain animal species. To address this shortfall, instrumentation has been deployed on wild animals to assess habitat, behavior and physiology. Many instrumentation systems acquire data on their host's location, locomotion, foraging behavior and physiological parameters such as stomach temperature and heart-rate. In the case of aquatic or marine species, diving behavior is also monitored with particular interest. However, the absence of contemporaneous visual observations has left scientists to infer much about the animal's life from rudimentary data.
Various animal-borne imaging systems have been deployed on wild animals to capture images revealing the animal's interaction with its environment. The animal to which the housing is secured serves as a host, carrying the system wherever it travels throughout the course of its daily activities. The visual information provided by such systems has generated unprecedented insight into how wild animals interact with their environment and has advanced research to levels unattainable through systematic human observation.
Systems for securing image and data capturing instrumentation to animals have existed in one form or another for a number of years. The goal has always been to develop a system able to withstand the harsh salt water environment that is home to numerous species of ocean-going animals, such as whales, sharks, dolphins, porpoises, tortoises, rays, walruses, seals and sea lions. That objective, however, had proven elusive to attain within a single system. Salt water is the primary bane of delicate instrumentation because of its corrosive effect and electrical conductivity. Another major consideration is the tremendous pressure imposed on the system by the depth of the water column. Any system incapable of withstanding the ocean depths will succumb under the pressure exerted by the water column, permitting salt water to threaten the instrumentation and data stored inside. Additionally, the lack of light penetration into the deeper reaches of the ocean presents another complicating factor in image capturing.
Prior animal-borne imaging and data systems provided a pressure-resistant housing having a cylindrical shape with a flat, circular rearward surface. Although simple in construction, those systems suffered from excessive hydrodynamic drag induced by a cavitation point created directly behind the flat rearward surface of the housing as the host towed the system through the water.
Prior systems having a flat rearward surface also suffered from a lack of positive buoyancy. Once a system loses positive buoyancy it will sink, possibly irretrievably, carrying with it any recorded data. Thus, a flotation aid made of syntactic foam had to be added to the cylindrical housing to force the system to the surface of the water after detachment from its host where it could be retrieved by triangulating its on-board radio beacon. The flotation aid was generally conical in shape with its circular base end being affixed to the flat, circular rearward surface of the cylindrical housing with screws such that the point of the cone-shaped flotation aid pointed generally away from the host's normal direction of forward movement. While such a flotation aid helped reduce the overall hydrodynamic drag of the system and induced positive buoyancy, it suffered from several undesired drawbacks. The syntactic foam flotation aid increased the overall size of the system, yet because it was external to the pressure-resistant housing, it did nothing to increase the useable storage space for instrumentation. Even worse, the flotation aid was prone to inadvertent detachment from the housing due to strain induced by the locomotion of the host animal. Certain species of sharks and dolphins, for example, perform highly hydrobatic maneuvers that could detach the flotation aid used in prior systems.
Earlier designs also suffered from drawbacks in the way in which the primary components of the housing were held together. The forward surface of the cylindrical housing was a generally hemispherical or dome-shaped nose cone of about the same diameter as the cylindrical housing. The nose cone incorporated a translucent view port through which a video camera or other similar image-capturing device, affixed generally in alignment with the longitudinal axis of the cylindrical housing, could obtain images. In prior designs, the nose cone was secured to the housing by straps running the length of the housing and terminating in snap hasps that secured the nose cone in place. This means for securing the nose cone to the housing compromised the physical integrity and thus pressure resistance of the system. It could apply only limited compressive force to seal the two components to one another and the snaps were easily damaged. Moreover, the straps and snap hasps also added undesired hydrodynamic drag to the system.
Harnessing an animal-borne instrumentation housing to its host presents further challenges. A well-known device used to attach instrumentation to wild animals, such as sharks and whales, is the FLOY tag, a barb-like stainless steel pin that penetrates the host's flesh and remains imbedded in the host long after the instrumentation is detached from the externally-protruding portion of the FLOY tag. Ethical concerns often inhibit the use of invasive devices, particularly in connection with endangered or threatened species which would otherwise stand to reap many potential benefits from knowledge attained using animal-borne instrumentation systems. Simple suction cups molded from a resilient is compound such as rubber impart little or no harm to the host and have been employed with a small degree of success under certain conditions. However, simple suction cups do not create a sufficient internal vacuum to hold an instrumentation system to the host for more than a short time. Moreover, simple suction cups are easily detached by the host's hydrobatic maneuvers or its contact with other animals or objects.
Thus, there exists a continuing need for an animal-borne instrumentation system having low hydrodynamic drag, positive buoyancy and a sturdy construction. The system should also minimize the potential interference with the host's health, mobility and lifestyle.